1. Technical Field
The present invention relates to a rotor which includes a rotor core formed into a predetermined shape by arranging in a circumferential direction and stacking in a stacking direction a plurality of core segments, and to a rotating electric machine which includes the rotor.
2. Description of Related Art
Conventionally, in consideration of centrifugal force, rotors for rotating electric machines generally employ cores that are formed into one piece by, for example, blanking.
On the other hand, there is disclosed, for example in Japanese Patent Application Publication No JP2002262496A, a rotor core that is formed of core segments and designed to withstand centrifugal force. More specifically, the rotor core includes a plurality of cylindrical cores. Each of the cylindrical cores is formed by stacking a plurality of annular cores. Each of the annular cores is formed by arranging in a circumferential direction a plurality of fan-shaped core segments that have protrusions and recesses formed in circumferential end surfaces thereof and fitting each of the protrusions into a corresponding one of the recesses to form one protrusion-recess fitting portion. Moreover, the cylindrical cores are stacked so that the protrusion-recess fitting portions in any of the cylindrical cores are circumferentially offset from those in another of the cylindrical cores.
However, with the above configuration, the roundness (e.g., the inner and outer diameters) of the rotor core depends on the positional accuracy (or fitting accuracy) of the protrusion-recess fitting portions. Therefore, increasing the roundness of the rotor core will result in an increase in the manufacturing cost as well as an increase in the maintenance cost of dies. Moreover, when the core segments are formed at high accuracy, the fit between the protrusions and the recesses is close to interference fit. Therefore, it is not easy to perform the assembly process of the rotor core.
On the other hand, when the core segments are formed at low accuracy, the coaxiality of the rotor core with a stator is low. Therefore, it is inevitable to increase the size of an air gap provided between the rotor core and the stator, thus lowering the performance of the rotating electric machine.